Students have just learned how to write and correctly balance chemical equations. This lesson will introduce them to three of the five types of chemical reactions. Students will learn to identify these reactions by recognizing patterns of chemical behavior. Recognizing patterns of behavior among reactions will be important in predicting the products of reactions. Today's focus will be on combination, decomposition, and combustion reactions. They will rotate through stations to practice identifying and balancing these various reactions. One station will review balancing chemical equations, another will allow students practice in predicting products of reactions, and the last one will provide a real-world application of the reactions.
Objectives
Students will…
Identify a reaction as combination, decomposition, or combustion.
Compare/contrast the types of chemical reactions.
Predict the products of combination, decomposition, or combustion when reactants are given.
Analyze the various reactions they encounter (at each station) and distinguish which type of reaction it is.
Materials
iron filings
bunsen burner
Bic lighter
detergent, hydrogen peroxide, KI OR youtube video(attached below)
ball and stick models kit
Station Direction Sheets (attached below)
old pennies, vinegar, salt, beakers
Homework worksheet (attached below)
Instruction
Opening (15 minutes)
Do-Now: Take out homework. Open textbook to p.212 and read the sections titled Combination Rxns, Decomposition Rxns, and Combustion Rxns.
Go over correct answers to homework worksheet. Worksheet will be displayed on the SmartBoard. I will have a one or two students come up and write in their answers to the HW. If other students did not get the same answers, or the answers are incorrect, we will review and correct the problems.
(If not done yesterday, hand out Adopt-a-Chem Rxn assignment and read over the assignment as a class). Make sure students don't have any lingering questions about the requirements of the assignment.
Explain the purpose of today's lesson: introducing the different types of chemical reactions, recognizing similarities and differences among the types, classifying given reactions, predicting products based on type of reaction
Have students examine their homework assignment and come up with some similarities and difference among the reactions. This will help lead into the discussion about combination, decomposition, and combustion.
Middle (60 minutes)
Activity 1: 25 minutes
This will be an interactive discussion between the students and I. I will tell them which information they need to write in their notes. I will perform each demonstration, while asking the probing questions (shown below). Then, as a class we will summarize (on SmartBoard/ in notebooks) the chemical reaction that was demonstrated. The characteristics of each reaction and the general form will be identified and written, as will be a quick picture the can remind the students of the demonstration I have just done.
Demonstration: Burn iron filings (4Fe + 3O2 -> 2Fe2O3)
Ask probing questions: How many reactants are present? How many products are there? What can we conclude about this reaction (2 combine to form 1)? What is a reaction that we discussed yesterday that satisfies these characteristics (H2 + O2)? Are we combining or breaking down? That is why this type of chemical reaction is classified a combination reaction, A + B -> AB.
Demonstration: 50mL detergent, 100mL 30% hydrogen peroxide, 10mL of water with 10g KI (H2O2 -> H2O + O2)
Ask probing questions: If H2O2 is the chemical formula for hydrogen peroxide, what could the products be? So if we started with one reactant and ended up with 2 products, did we combine or break down compounds? This type of reaction is called a decomposition reaction, AB -> A + B.
Demonstration: Bic lighter or Bunsen burner
Ask probing questions: What is the liquid in the lighter reacting with? What is being produced, a gas, liquid, or solid? If I knew the gases were water vapor and carbon dioxide, what elements must the liquid be composed of? So we can conclude that when fuel(or hydrocarbon) reacts with oxygen, carbon dioxide and water are formed, CH + O2 -> CO2 + H2O. This reaction of elements and compounds with oxygen is known as combustion and it always releases energy.
Reflective question: What other reaction demonstrated today could also be considered a combustion reaction (Iron in oxygen)?
Activity 2: 35 mins (~12 minutes at each station)
Stations- students will work in groups of 4 which they will choose. Each station will be available at every lab bench so that students can proceed to different stations when they are ready.
Station 1: Practice Balancing Equations- combination, decomposition, and combustion reactions
On the Station Sheet there will be several word equations. Students will convert the word equations to balanced chemical equations. They will also identify which type of chemical reaction is shown.
Station 2: Real-World Applications
Students will be given vinegar, salt, old pennies, and a bowl. They will follow the directions on the Station page (attachment above). They must identify what is occurring, and identify the type of reaction it is.
Station 3: Predicting Products
Students will have the ball-and-stick model kit. They will be given a list of reactions (reactants only). Using the kit and their knowledge of combination, decomposition, and combustion reactions, they will construct the model(s). This requires them to determine the type of reaction, then decide the probable products. They will be given a summary chart to aid them in predicting products.
Bic lighter is burning butane in oxygen
bunsen burner is burning methane in oxygen
Why did the vinegar and salt clean the pennies? Copper atoms can combine with oxygen atoms from the air to make a molecule called copper oxide. The pennies looked dull and dirty because they were covered with copper oxide. Vinegar is an acid which reacts with the salt to remove copper oxide(what was making your pennies dull). The pennies that were rinsed with water after soaking in vinegar were protected from further reactions of copper and oxygen. The unrinsed pennies turned greenish-blue because the vinegar and salt dissolved the copper-oxide layer, making it easier for the copper atoms to join oxygen from the air and make a chemical called malachite. This experiment would also work if you used salt and lemon juice or orange juice because those juices are acids too.
Copper carbonate is created when copper is in the presence of carbon dioxide and water 2 Cu (s) + H2O (g) + CO2 + O2 → Cu(OH)2 + CuCO3 (s)
Lesson #2: Classifying Chemical Reactions I
Summary
Students have just learned how to write and correctly balance chemical equations. This lesson will introduce them to three of the five types of chemical reactions. Students will learn to identify these reactions by recognizing patterns of chemical behavior. Recognizing patterns of behavior among reactions will be important in predicting the products of reactions. Today's focus will be on combination, decomposition, and combustion reactions. They will rotate through stations to practice identifying and balancing these various reactions. One station will review balancing chemical equations, another will allow students practice in predicting products of reactions, and the last one will provide a real-world application of the reactions.Objectives
Students will…
Identify a reaction as combination, decomposition, or combustion.Compare/contrast the types of chemical reactions.
Predict the products of combination, decomposition, or combustion when reactants are given.
Analyze the various reactions they encounter (at each station) and distinguish which type of reaction it is.
Materials
iron filingsbunsen burner
Bic lighter
detergent, hydrogen peroxide, KI OR youtube video(attached below)
ball and stick models kit
Station Direction Sheets (attached below)
old pennies, vinegar, salt, beakers
Homework worksheet (attached below)
Instruction
Opening (15 minutes)
Middle (60 minutes)
Activity 1: 25 minutesActivity 2: 35 mins (~12 minutes at each station)
Closing (15 minutes)
Notes
Bic lighter is burning butane in oxygenbunsen burner is burning methane in oxygen
Why did the vinegar and salt clean the pennies?
Copper atoms can combine with oxygen atoms from the air to make a molecule called copper oxide. The pennies looked dull and dirty because they were covered with copper oxide. Vinegar is an acid which reacts with the salt to remove copper oxide(what was making your pennies dull). The pennies that were rinsed with water after soaking in vinegar were protected from further reactions of copper and oxygen. The unrinsed pennies turned greenish-blue because the vinegar and salt dissolved the copper-oxide layer, making it easier for the copper atoms to join oxygen from the air and make a chemical called malachite. This experiment would also work if you used salt and lemon juice or orange juice because those juices are acids too.
Copper carbonate is created when copper is in the presence of carbon dioxide and water 2 Cu (s) + H2O (g) + CO2 + O2 → Cu(OH)2 + CuCO3 (s)
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